To undertake this side quest from Scribe Bigsley, head over to Rivet City. Though it's close to Bigsley's location at Jefferson Memorial, the easiest way to get to Rivet City is to, of course, travel there immediately via your Pip-Boy. When you arrive, you'll find the person you seek, a woman named Officer Lepelletier, roaming around the entrance ramp to the city. So if you fast travel to this location, don't go towards Rivet City itself, but rather, go away from it. When you track her down, speak with her and she'll tell you what she needs you to do. A caravan leaving Project Purity (the Jefferson Memorial) is headed north with water. She's positive that a group of bandits that have been harassing recent caravans will attack this one, and she wants you to go with the caravan to figure out who's at the bottom of the harassment. Then, you'll get to put an end to it.

After your conversation with her runs its course, use your Pip-Boy to instantaneously travel to the Jefferson Memorial. Then, seek out the bridge leading due northward from the surrounding environs of the memorial. Keep walking north... keep on going. You'll need to head northward over the bridge and continue northward for some time. Eventually, you'll run into a couple of bandits attacking the water-carrying caravan. While the Rivet City security detail is doing its best to keep these guys at bay, you'll be able to quickly turn the tide of the battle in their favor. When you've felled both Bandits, scour their bodies for voice recordings that will give away their location. So where are these guys holed up? Wilhelm's Wharf, a location due north on the far side of the Potomac River, a place you've likely found already, and thus can travel to instantaneously with no issue.

When you arrive at Wilhelm's Wharf following the massacre of the water bandits, you'll find a group of bandits and an old woman (the latter of which is an occupant of this area during the main game). The leader of the bandits is a man named Split Jack. And as you'll soon find out, Split Jack is all talk and no game. He controls a motley crew of thugs that rob caravans and other shipments around the Capital Wasteland, but it won't take long for you to get under Split Jack's skin. However, your crap talk might not have the desired effect, for he'll hand over some goods to you thinking that you might be interested in joining them.

Show Split Jack that you have no such intentions, however. When your conversation with him runs its course, open fire on him and the rest of his weak crew. It won't take long to eradicate the entire group of enemies, especially if you're doing this after Broken Steel's main quest, and thus are equipped with the ultra-powerful Tesla Cannon. Once all enemies are felled, you'll need to teleport back to Rivet City, where you can report to Officer Lepelletier. While she's thankful for your work, she won't have anything to reward you with. So, you'll need to then teleport over to the Jefferson Memorial, where you can speak with Bigsley to conclude this side quest.